1. Field of the Invention
The present invention relates to a internal combustion engine control system for vehicle that, when any state of excessive power generation due to abnormality of a vehicle generator occurs, detects the state and controls engine speed of an internal combustion engine and a battery load thereby suppressing over-voltage in electric system.
2. Background Art
A power supply for vehicle is generally constituted of a vehicle generator and a battery to be charged by the vehicle generator, and is arranged such that output from the vehicle generator may be controlled in accordance with a charged state of the battery. Further, to improve reliability of the vehicle, it is a recent trend to employ a system in which an internal combustion engine control apparatus for supervising and controlling the internal combustion engine mounted onto the vehicle sets a target voltage of the vehicle generator according to a traveling state of the vehicle, and controls the output from the vehicle generator in conformity with this target voltage. In such a vehicle generator, it is possible that the vehicle is led into an incapability of traveling in the case of occurring abnormality due to any trouble in generated voltage. Accordingly, various attempts of coping with the abnormality in the generated voltage have been heretofore proposed.
FIGS. 10 and 11 show one example of the manner of coping with such trouble in the conventional vehicle generator. FIG. 10 is a schematic diagram of an electric system of the vehicle, and FIG. 11 is a functional block diagram of the internal combustion engine control apparatus. An internal combustion engine 1 mounted on the vehicle is controlled by an internal combustion engine control apparatus 2 in accordance with a variety of information, and drives the vehicle as well as drives a vehicle generator (AC generator) 3. Output from the vehicle generator 3 charges a battery 4 and, at the same time, supplies a power to various electric loads. As partially shown in FIG. 10, there are electric loads such as a head light 5, a heater heating wire 6, a cooler compressor motor 7 and the like. These electric loads are turned ON/OFF by operation of switches 8 provided at a driver's seat of a vehicle. Further, electric loads such as an electronic device 9 including a control device for the traveling system or other electronic device 10 are used.
The internal combustion engine control apparatus 2 includes constituting elements and functions such as a unit power supply generation section 11 to which a power is supplied from the battery 4 thereby forming a power supply for itself, battery voltage monitor means 12 for monitoring a battery voltage to perform a fuel injection control, maximum engine speed limiting means 13 for preventing the internal combustion engine 1 from over engine speed, and engine control means 14 for controlling the internal combustion engine 1 including an output from the maximum engine speed limiting means 13. The internal combustion engine control apparatus 2 includes further elements such as power generating state monitor means 15 for monitoring, e.g., a voltage generated by the vehicle generator 3 in response to a signal from a voltage control device incorporated in the vehicle generator 3, over-voltage determination means 16 for determining an over-voltage of the vehicle generator 3 on the basis of the output from the power generating state monitor means 15, and failure alarm control means 17 for generating a failure alarm in response to the output from the over-voltage determination means 16.
In the conventional internal combustion engine control apparatus 2 including above elements and functions, in the case where any trouble occurs at the vehicle generator 3 and the output voltage becomes an over-voltage or under-voltage (power generation incapability), the over-voltage determination means 16 or under-voltage determination means (not shown) operates in response to the output from the power generating state monitor means 15, indicates the failure alarm using display means 19 such as a lamp or a light emitting diode, and tells the trouble to a driver. In the conventional apparatus, this alarm display is a final output from the power generating state monitor means 15, and any emergency measure for the failure is entirely left to the driver. For example, the Japanese Patent Publication (unexamined) No. 79981/1996 disclosed a technique like this, and in which the internal combustion engine control apparatus compensates the control of the generated voltage in accordance with a difference between a target voltage and a battery voltage, such that the failure is determined and abnormality is indicated in the case where a compensation value exceeds a threshold value.
On the other hand, another attempt different from the above-mentioned measures is disclosed, for example, in the Japanese Patent Publication (unexamined) No. 299123/1999. In the technique disclosed in this official gazette, the vehicle generator includes means for detecting the generated voltage, a dual voltage control device, and switching means for switching the dual voltage control device. In this arrangement, engine speed of the internal combustion engine and voltage generated by the vehicle generator are inputted. When the engine speed is not less than a predetermined value, and the output voltage is either less than a first predetermined value or is not less than a second predetermined value, it is determined that the voltage control device is in failure. Then, the currently using voltage control device is switched to a backup one, and an alarm is given to the driver as well.
In the case where the vehicle generator is in failure, either of the two phenomena, under-voltage (power generation incapability) and over-voltage (excess voltage) occurs. In time of the under-voltage, the traveling to some degree is possible on condition that the power charged in the battery has a reserve capability. On the contrary, in the case of over-voltage, charge amount for the battery increases, and the battery voltage abnormally rises when the charge amount exceeds a limit. This abnormal rise of the battery voltage not only extremely shortens the life of battery but also a high voltage will be applied to the vehicle-mounted electronic devices. Moreover, when continuing such a high voltage state, a secondary failure incapable of being restored will occur in the electronic devices. The failure in the electronic device is led into traveling incapability of the vehicle, and the abnormal rise in the battery voltage induces generation of a poisonous gas and explosion thereof. Therefore the failure of over-voltage is a trouble to be prevented by all means. In addition, it is essential to make the vehicle generator small in size and light in weight. From this viewpoint, it is actually difficult to achieve dual system of the voltage control device incorporated in the vehicle generator as described in the known art.